The invention relates to a contact pin for a printed circuit board, comprising a mounting portion for mounting the contact pin in a hole in the printed circuit board, said mounting portion having a first outer leg, a centre leg and a second outer leg, each leg extending in the longitudinal direction of the contact pin, at least the outer legs joining a solid contact pin portion at both ends, the centre leg lying with its inwardly directed part between the outer legs.
Such a contact pin is known from U.S. Pat. No. 4,066,326. At this known contact pin both outer legs are bent radially outwardly in the opposite direction from the centre leg, wherein seen in cross section, the centre of the circle touching the outer side of each of the legs lies on the longitudinal axis of the contact pin. When the contact pin is inserted into a hole, the legs move towards each other in a direction parallel with the symmetry plane of the contact pin. Because the legs are at least partially moved back to their original position, forces extending substantially in the longitudinal direction of the contact pin are exerted on the ends of the legs, which forces result in a moment exerted on the ends of the contact pin whereby these ends are pivoted out of the original straight position. Thereby, the position of the ends of the contact pin with respect to the hole in which the contact pin is inserted, is not determined accurately anymore. When a wire wrap connection should be made with the end of the contact pin, the tool for making this connection cannot be brought in register with the corresponding end of the contact pin in the right manner anymore and this end could be bent. The same problem occurs when a connector should be mounted on the ends of an array of such contact pins.
Further the pivoting movement of the ends of the pin results in a collapsing of the legs as seen in cross section, so that the contact surface between the legs and the hole is only minimal and, moreover, this contact surface is only located at the insertion side of the hole where the stresses in the printed circuit board are at a maximum.
As the legs of the contact pin move mainly in the longitudinal direction through the hole, material scraped off of the lining of the wall and of the mounting portion of the contact pin, is pushed out of the hole. This material could cause a short-circuiting.
European patent application 0 105 044 relates to a contact pin of the above-mentioned kind wherein it is attempted to obviate said disadvantages by making the outer legs so that besides the movement parallel with the symmetry plane of the contact pin a torsion of the outer legs occurs. However, experiments have shown that the disadvantages mentioned are not overcome in a satisfactory way by this contact pin.
U.S. Pat. No. 4,230,384 discloses a contact pin with a mounting portion consisting of two torsion legs joining a solid contact pin portion at both ends. This known contact pin has the disadvantage that if at insertion into a relatively small hole the facing sides of the legs will contact each other no further deformation of the mounting portion for adaptation to the diameter of the small hole is possible. At small holes this could easily result in a damage of the lining of the wall of the hole. Moreover, at this known contact pin the position of the pin in the hole depends on the diameter of the respective hole. As the dimensions of the solid contact pin portions are generally standardised, the dimensions of both legs of the mounting portion of this contact pin are fixed. In practice the rigidity of the legs appears to be substantially higher than is required for providing a sufficient retaining force of the contact pin in the hole. Thereby unnecessary high stresses are caused in the printed circuit board.